Transportation of fluids by means of circular pipes and the like is widely utilized in daily life and in the industrial field. In a fluid transport pipe that is constructed as a circular pipe, friction drag is the dominant drag with respect to the total drag acting within the pipe, and the friction drag increases markedly at a turbulent flow in comparison to a laminar flow. Accordingly, relaminarization from a turbulent flow to a laminar flow is effective for conserving energy during transportation of a fluid. In Patent Literature 1 that is mentioned hereunder, a technique is disclosed that causes the flow of a fluid flowing inside a pipe to pulsate by periodically accelerating and decelerating the flow of fluid by controlling a pump that pressure-feeds the fluid, and thus achieves a drag reduction effect (particularly, a friction reduction effect) by relaminarization of the flow.
Further, in each of Non Patent Literatures 1 and 2 mentioned hereunder, a fluid transport pipe is described that is configured so as to obtain a drag reduction effect without requiring the above described pump control by adopting a pipe shape in which a channel cross-sectional area is periodically enlarged and reduced in a flow direction (direction of fluid movement within the pipe).